The Histopathology Core will evaluate histologic sections using standard stains and immunohistochemistry, western blots, tissue preparation and allocation for toxicology studies and biodistribution studies from all experimental studies done in mdx mice and Rhesus macaques monkeys described in Projects 1 and 2. The Histopathology Core is critical to the success of this U54 proposal for the following reasons: 1) The mission of each Project will be facilitated by the expertise of one lab with built in quality control measures to process all tissues in a consistent manner. 2) The objectivity of the results will be enhanced by separating the Pi's from the outcome measures. 3) There will be greater consistency between each of the Projects by having all tissue sections processed by the same staff. 4) Techniques available in the Histopathology Core are not common to all Pi's in each project. The Histopathology Laboratory will evaluate muscle following gene transfer from all projects to maintain consistency between projects.